A power line communication (PLC) indicates a communication method which transmits/receives a data signal via a power line, wired in a house or an office to supply power. Specifically, the PLC may be embodied by modulating a data signal into a high frequency signal, transmitting the modulated high frequency signal to an alternating current (AC) line, and separating and receiving the transmitted high frequency signal via a high frequency filter. In this instance, the high frequency filter has a cutoff frequency of about 50 Hz or about 60 Hz.
Since a network utilizing PLC technology can be constructed utilizing an existing wiring, a cost burden, which may be caused by a construction with additional wiring, may be reduced. Also, an expansion that can install an additional device to a network with only a plug-in, even after constructing the network, is guaranteed. Thus, the PLC technology is widely utilized for any type of wired/wireless network solutions.
In addition to the PLC technology, a hybrid fiber coax (HFC) is widely utilized. The HFC includes an optical fiber and a coaxial cable, and can transmit a data signal (e.g., for Internet, cable television, crime prevention, disaster prevention, remote inspection, and automatic control) to a broadcasting station and an optical network unit via the optical fiber, and from the optical network unit to a subscriber via the coaxial cable. Theoretically, the HFC may support a wide transmission band that can connect each channel with a bandwidth of about 6 MHz at a transmission speed between 9600 bps and 42 Mbps.
FIG. 1 is a diagram illustrating a configuration of a network 110 including a PLC system installed in a subscriber location and a subscriber network utilizing an HFC according to a conventional art.
According to the PLC system and the subscriber network utilizing the HFC according to the conventional art, as shown in FIG. 1, a cable modem terminal system (CMTS) 111 receives a data signal from a video on demand (VOD) system, a Voice over Internet Protocol (VoIP) system or an Internet network, converts the data signal into a data packet signal, and transmits the converted data packet signal and a cable television (CATV) signal to an optical transmitter OTX 114. The CATV signal is transmitted from a CATV system 112. In this instance, the CMTS 111, the CATV system 112, and the optical transmitter 114 connect with one another via a coaxial cable 113. Specifically, the data packet signal may be transmitted to the optical transmitter 114 via the coaxial cable 113.
The optical transmitter 114 converts the received data packet signal into an optical signal and transmits the converted optical signal to an optical network unit ONU 120 via an optical fiber 121. The optical network unit 120 reconverts the optical signal into the data packet signal and transmits the reconverted data packet signal to a cable modem 141 of a subscriber location 140 via a trunk bridge amplifier TBA 130. In this case, a frequency band of a CATV signal may be separated from the data packet signal and transmitted to a television (TV) via a set-top box STB.
The cable modem 141 converts the data packet signal into a data signal and transmits the converted data signal to a PLC modem 142. The PLC modem 142 converts the data signal into a signal corresponding to a predetermined PLC protocol, couples the converted signal with a power line 143 to be transmitted to at least one communication terminal installed in the subscriber location 140.
Another PLC modem 144 is installed in each of the at least one communication terminal. The PLC modem 144 extracts the data signal from the PLC signal which is transmitted via the power line 143, and transmits the extracted data signal to each of the at least one communication terminal. In this instance, the communication terminal may include a home automation device, a personal computer (PC), a game device, a security system, and the like.
In a PLC system according to the conventional art, a home network utilizing an HFC may be constructed by utilizing only a previously installed power line, without installing additional wiring to a subscriber location. However, as described with FIG. 1, only when the cable modem 141 and the PLC modem 142 are separately installed in the subscriber location 140, a subscriber of a PLC service may utilize the PLC service utilizing the HFC. Also, only when protocol conversion according to a communication protocol between the power line 143 and the PLC modem 142 is performed in the subscriber location 140, the cable modem 141 and the PLC modem 142 may transmit/receive a signal with an external location.
Also, when the PLC system utilizing the HFC is constructed as described above, a data packet signal is required to be transmitted/received via the trunk bridge amplifier 130 and thus the data packet signal may be significantly attenuated.
Also, so that a communication terminal installed in a first subscriber location may communicate with another communication terminal installed in a second subscriber location, protocol conversion has to be performed via a PLC modem installed in each subscriber location. Also, the protocol converted signal has to pass through a CMTS.
Accordingly, the development of a PLC system utilizing an HFC which can outperform the conventional art, and utilize an existing HFC and a power line as is, and can perform more stable communications without performing a PLC protocol conversion and applying a PLC frame in each subscriber location, and prevent an attenuation in a signal caused by a trunk bridge amplifier, and can also readily interoperate with a PLC network in the each subscriber location is required.